* autoconf/aclocal.m4: upgrade to autoconf-2.52 infrastructure,
sync with CLisp from CVS.
* autoconf/autoconf: Likewise.
* autoconf/autoconf.m4f: Likewise (new file).
* configure.ac: Likewise (new file, replaces configure.in).
* configure.in: Likewise (deleted, replaced by configure.ac).
* autoconf/config.{guess,sub}: Update to GNU version 2001-12-13.
* src/Makefile.in: made VPATH safe for autoconf-2.52.
* include/cln/config.h.in: Add __s390__.